Chapter 18 The Digestive System

Ch 18.1 - Nutrition A. Your body needs nutrients found in foods 1. Nutrients provide energy and materials for cell development 2. You need energy for every activity and to maintain a steady internal temperature

B. Classes of Nutrients 1. Proteins a) Used for replacement and repair of body cells and for growth b) Made up of amino acids c) Essential amino acids supplied by food d) Found in eggs, milk, cheese and meat

2. Carbohydrates a) Main source of energy for your body b) Made of carbon, hydrogen and oxygen c) Sugars are simple; starch & fiber complex - Sugars found in fruits, honey, milk - Starches found in potatoes and pasta - Fiber found in whole-grains and veggies

b) Stores excess energy c) Helps body absorb vitamins 3. Fats a) Also called lipids b) Stores excess energy c) Helps body absorb vitamins d) Classified as saturated & unsaturated - Saturated solid at room temp, clog blood vessels and associated with high cholesterol - Unsaturated liquid at room temp, and not associated with health risks

a) Needed for growth, regulating body functions and preventing disease 4. Vitamins a) Needed for growth, regulating body functions and preventing disease b) A well-balanced diet usually gives your body all the vitamins it needs c) Two groups: water soluble & fat soluble - Water: Vitamins B & C - Fat: Vitamins A, D, E & K B – growth, nervous system health, RBC production; eggs, dairy, vegetables C – healthy bones, teeth, immune system, wound recovery; fruits & vegetables A – eyesight, healthy skin; dairy, meat, fruits, vegetables (carrots) D – absorption of calcium for teeth and bones; dairy & fish E – formation of cell membranes; eggs, nuts, oils K – blood clotting; vegetables

5. Minerals a) Inorganic nutrients needed in small amounts b) Regulate many chemical reactions in the body c) Calcium and Phosphorus used most

6. Water a) Required for survival b) Cells need water to carry out their work c) Dissolves other nutrients d) Human body is about 60% water e) Lost each day when you perspire, exhale, and get rid of wastes

C. Food Groups 1. Because no food has every nutrient you need to eat a variety of foods 2. The food pyramid is a tool to help people select foods that supply all the nutrients they need 3. Foods that contain the same nutrients belong to a food group

4. Five food groups: a) Bread and Cereal b) Fruit c) Vegetable d) Dairy e) Meat, Poultry, Fish & Beans

Ch 18.2 – Digestive System A. Digestion – process of breaking down food into small molecules to be absorbed 1. Mechanical Digestion – when food is physically chewed, mixed and churned 2. Chemical Digestion – when food is broken down by chemical reactions

B. Enzymes 1. Type of protein that speeds up rate of chemical reactions in your body 2. Many enzymes are involved in the digestion of carbs, proteins and fats

C. Organs of the digestive system 1 C. Organs of the digestive system 1. Accessory organs – aid in digestion but food does not pass through them a) tongue, teeth & salivary glands

b) Liver – produces bile for the stomach which breaks up ingested fats c) Gallbladder – small sac that stores bile produced by the liver

d) Pancreas – produces insulin which allows the body to process carbohydrates (sugars)

2. Digestive Tract – organs that food does pass through during digestion a) Mouth – here accessory organs change food into a soft mass called a bolus

b) Esophagus – muscular tube that moves food to the stomach using waves of muscle contractions called peristalsis

c) Stomach – muscular bag that digests food mechanically by peristalsis and chemically with digestive solutions of HCl acid; food becomes a thin, watery fluid called chyme

d) Small Intestine – nutrients are absorbed from chyme into the blood; projections called villi increase surface area for absorption Ave. adult length – 7m/23ft

e) Large Intestine – water absorbed from undigested chyme; peristalsis slows so chyme may remain here as long as 3 days Ave. adult length – 1.5m/5ft (but wider diameter)

f) Rectum & Anus – end of large intestine and opening to outside of body; controls release of remaining solid wastes

D. Bacteria live in many organs of the digestive tract helping to break down food and make vitamins ESCHERICHIA COLI is a type of bacteria that lives in the intestinal tract, aiding the digestive process by suppressing the growth of harmful bacteria and synthesizing vitamins.